Every summer, marine biologists have
come to expect the formation of a huge band of nearly
lifeless ocean off the coast of Louisiana in the Gulf
of Mexico. This area, called a "dead zone",
kills or drives off fish, crustaceans, and other sea
life because it is so depleted of oxygen.

The condition of oxygen depletion
is known as hypoxia. Hypoxia results in dead zones worldwide,
but the one in the Gulf of Mexico is the largest. The
size of the dead zone in the Gulf changes every year.
In 1988, a year of drought, the dead zone was relatively
small. In 1993, a year of flooding on the Mississippi
River, the dead zone was quite large. In the summer
of 1999, the dead zone in the Gulf of Mexico was 20,000
square kilometers, an area about the size of New Jersey.

! Move your cursor over the satellite
image to see the area of the dead zone in 1999. Click
the highlighted zone to see a photograph of the dead
zone viewed from a boat.

Space Science and Engineering
Center, University of Wisconsin, Madison

This satellite image
shows plumes of sediments emptying into the Gulf
of Mexico from the Mississippi River.